Structural,textural, surface chemistry and sensing properties of mesoporous Pr,Zn modified SnO2–TiO2 powder composites

Mesoporous Zn and Pr modified SnO₂-TiO₂ mixed powders (Sn:Ti:Zn:Pr contents 60:20:15:5) have been prepared by a modified sol–gel method involving Tripropylamine (TPA) as chelating agent, TritonX100 as template and Polyvinylpyrrolidone as dispersant and stabilizer, respectively. The obtained gels have been dried at different temperatures and calcined in air at 600 and 800 °C, respectively. Phase identification of the synthesized samples and their evolution with the calcination temperature has been performed by X-ray diffraction. N₂ adsorption/desorption isotherms were found to be characteristic for mesoporous materials, showing relatively low values for the specific surface area (15–32 m² g⁻¹) and nanometric sized pores. In case of the sample calcined at 800 °C, a bimodal pore size distribution can be observed, with maxima at 20 and 60 nm. SEM results demonstrate a porous nanocrystalline morphology stable up to 800 °C. The surface chemistry investigated by XPS reveals the presence of the elements on the surface as well as the oxidation states for the detected elements. At 800 °C a diffusion process of Sn from surface to the subsurface/bulk region accompanied by a segregation of Ti and Zn to the surface is noticed, while Pr content is unchanged. The sensing properties of the prepared powders for CO detection have been tested in the range of 250–2000 ppm and working temperatures of 227–477 °C.     

Preparation and electrochemical performance of SnO2@carbon nanotube core–shell structure composites as anode material for lithium-ion batteries

Carbon nanotube-encapsulated SnO₂ (SnO₂@CNT) core–shell composite anode materials are prepared by chemical activation of carbon nanotubes (CNTs) and wet chemical filling. The results of X-ray diffraction and transmission electron microscopy measurements indicate that SnO₂ is filled into the interior hollow core of CNTs and exists as small nanoparticles with diameter of about 6 nm. The SnO₂@CNT composites exhibit enhanced electrochemical performance at various current densities when used as the anode material for lithium-ion batteries. At 0.2 mA cm^?2 (0.1C), the sample containing wt. 65% of SnO₂ displays a reversible specific capacity of 829.5 mAh g^?1 and maintains 627.8 mAh g^?1 after 50 cycles. When the current density is 1.0, 2.0, and 4.0 mA cm^?2 (about 0.5, 1.0, and 2.0C), the composite electrode still exhibits capacity retention of 563, 507 and 380 mAh g^?1, respectively. The capacity retention of our SnO₂@CNT composites is much higher than previously reported values for a SnO₂/CNT composite with the same filling yield. The excellent lithium storage and rate capacity performance of SnO₂@CNT core–shell composites make it a promising anode material for lithium-ion batteries.     

液相直接沉淀法制备纳米SnO2

在单因素实验和Box-Behnken实验设计基础上,利用响应面分析法,对影响纳米SnO2收率的工艺条件进行优化研究,验证实验显示,得到的最优条件能够很好地符合预测值。通过单因素和响应面分析实验,得到了纳米SnO2最优工艺参数:水解温度80℃、水解时间44 min、滴加浓度为0.84 mol/L的SnCl4.5H2O 27 mL反应,产物在700℃下煅烧180 min。SnO2平均收率可达99.77%,平均粒径为23.6 nm。取得的最优工艺条件可以很好地用于纳米SnO2的生产,具有一定的理论与实用价值。     

SnO2溶胶体系稳定性实验研究

SnO2线性聚合物溶胶液是掺杂SnO2功能膜Sol-Gel制备工艺的基础。本文以Sn(OBun)4为前驱体。AcacH为稳定剂,BunOH为溶剂,用Sol-Gel方法成功地合成出SnO2无机线线性聚合物,并对acacH稳定剂的作用机理、加水量的多少对SnO2溶胶稳定性的影响进行了研究。结果表明:Sn(OBun)4具有较高的水解活性,在H2O的亲核取代进攻下,迅速水解并快速团聚沉淀,必须通过稳定剂对Sn(OBun)4进行改性降低其活性才能制备出稳定的溶胶液。乙酰丙酮(acacH)通过与Sn(OBun)4形成六配位螯合中间体Sn(OBun)2(acac)2,降低原单体水解活性机理来稳定Sn(OBun)4单体。在一定acacH稳定下(如acacH比为2),过量的H2O加入会破坏其稳定作用,使溶胶液迅速水解,快速团聚沉淀;而加水量过少,Sn(OBun)2(acac)2改性单体水解困难,体系不能形成溶胶液。     

SnO2纳米粉体的制备及分散

采用溶胶-凝胶法制备SnO2纳米粉体并检测其分散效果.用锡粒与柠檬酸(1:2、1:4)在pH为5～6条件下,通过水浴、干燥、煅烧等步骤制备出具有四方金红石结构的SnO2纳米粉体,利用热分析仪、透射电镜、X射线衍射仪对材料进行表征,并研究搅拌时间、分散体系pH值对纳米SnO2粉体分散稳定性的影响.结果表明:柠檬酸量的增加...     

SnO2气敏材料的研究进展

SnO2气敏传感器具有元件制作简单、使用寿命长、稳定性好、对气体的响应时间短等优点,已成为一个重要的研究课题.气敏反应是气体与材料表面接触后发生的化学反应,因此材料的表面组成、掺杂改性、缺陷分布、比表面积等都会影响材料的气敏性能.本文综述了近年来SnO2气敏材料的不同制备方法,以及金属氧化物和贵金属掺杂的SnO2气敏材...     

浅析SnO2电极安全使用问题

简述SnO2电极的使用安全电流,控制SnO2电极的电流上升速率及电压上限,SnO2电极的水套安装,烤窑时SnO2电极的保护。     

SnO2基可燃气体陶瓷传感器

本文给出了ＳｎＯ２基可燃气体陶瓷传感器的制备方法,该传感器显示出高灵敏度、高可靠性,短的相应时间和良好稳定性;讨论了通过添加金属氧化物以改善传感器特性的可能。     

纳米SnO2的表面改性研究

用超声处理与偶联剂相结合对纳米SnO2进行表面改性,用沉降体积、激光粒度分析、红外光谱(FTIR)和透射电镜(TEM)等手段时改性效果进行表征。研究了偶联剂的种类和用量等因素时改性效果的影响,并时改性机理进行了初步探讨。结果表明：钛酸酯偶联剂(CT-201)对纳米SnO2的改性效果比硅烷偶联剂(KH-550)好,其最佳用量为纳米SnO2粉体质量的6．5％～7．5％;经钛酸酯偶联刑改性的纳米SnO2在有机溶剂中的分散性大为改善;偶联刑与纳米SnO2之间的作用主要为化学吸附。     

溶胶—凝胶法制备SnO2光学薄膜

利用溶胶－凝胶法制备掺Ｓｂ与未掺Ｓｂ的ＳｎＯ２光学薄膜，测定了环境相对湿度ＲＨ与薄膜透过度，薄膜电阻率，Ｓｎ／Ｓｂ比与透光度和电阻率关系曲线。利用扫描电镜观察了薄膜的表面结构。     

SnO2纳米材料气敏性能的研究进展

近年来,金属氧化物半导体气敏传感器已经广泛地应用于人们的日常生活中,并成为传感器领域的重要分支。其中,SnO_2是最早被研究的一类气敏材料,属于典型的n型半导体金属氧化物,具有制备简单、成本低廉、性质稳定等优点。主要介绍了SnO_2纳米材料气敏性能的研究进展,详细描述了该材料的气敏机理、改性手段,并对其实用化的前景进行了展望。     

SnO2溶胶系水解缩合实验研究

通过加入稳定剂、催化剂，由锡酸四丁酯Sn(OBu^n)4制备出稳定的SnO2溶胶液，并有效地控制其Sol-Gel过程，同时测量Sol-Gel过程中SnO2溶胶液pH，粘度η随时间动态变化关系及凝胶时间Tg，对凝胶液稳定性、acacH稳定作用机理、催化机理、SnO2胶粒分形结构进行了研究分析，结果表明：acacH与Sn(OBu^n)4形成双螯合中间体，降低锡酯单体水解活性而使胶粒稳定生长，导致胶粒的准线性无机聚合物特性，催化剂阴离子通过对acac-螯环的部分取代反应，旋即水解、缩合，生产催化作用，阴离子尺寸大小支配催化作用强弱，溶胶液pH平稳值及Sol-Gel过程速度，流变学实验数据分析发现：溶胶液特性粘度[η]很好地符合近似线性模型，改性单体官能度f≈2.0,SnO2胶粒为准线性分子链，分型维度D≈1.80,分形结构介于自回避无规链(SAW)和无规高斯链之间。     

Ceramic varistors based on ZnO–SnO2

Model ceramic varistor formulations based on 98% ZnO–SnO₂ (plus 2% oxides of Bi, Co and Mn) were prepared by conventional powder processing routes; specimens were sintered at 1150–1275 °C. The product density increased with SnO₂ content, but decreased with increase in sintering temperature. The microstructures contained ZnO, Zn₂SnO₄ spinel and very small bismuth rich phases; with increasing Sn content the spinel became the dominant phase. From I–V measurements, the non-linear coefficients were found to be in the range 24–32. For all compositions, the α values decreased with increasing sintering temperature; the maximum α value was obtained with samples containing 20 mol% SnO₂ sintered at 1200 °C. Breakdown fields were in the range 3000–11000 V/cm and increased with increasing tin content. Leakage currents were in the range 1–11 μA. Tin substitution for Zn appears to cause a strong donor effect.     

纳米SnO2微粒的制备及其表征

以SnCl4.5H2O为原料,用水热合成法制备粒度均匀的纳米SnO2微粒。研究了反应物浓度、反应时间、反应温度等因素对SnO2微粒尺寸的影响。用DSC研究SnO2微粒的热性能,用激光光散射仪和透射电镜分析和观察SnO2微粒尺寸的影响。用DSC研究SnO2微粒的热性能,用激光光散射仪和透射电镜分析和观察SnO2微粒的形态和尺寸。     

F掺杂SnO2纳米粉体的燃烧合成

以金属锡和HF为原料采用燃烧合成法合成得到了F掺杂SnO2纳米颗粒。燃烧反应中甘氨酸为燃料,硝酸为氧化剂。采用XRD,BET,TEM和EDS等分析手段对合成得到的FTO进行了表征。结果显示,F的掺杂促进了SnO2基体晶粒的长大,所得到的粉体团聚较少,呈单分散状态。     

改性SnO2电极电催化降解煤化工废水

针对煤化工废水生化处理后无法达到污水排放和回用标准等问题,研究采用电催化氧化法降解废水中氨氮和COD来实现废水的零排放。比较了改性SnO_2电极(ESIX-SnO_2)与Ti/SnO_2电极电化学性能,并考察电流密度、初始pH、初始Cl-质量浓度对电催化降解废水中氨氮和COD的影响。结果表明,与传统的Ti/SnO_2电极相比,ESIXSnO_2电极晶粒尺寸变小、析氧电位(1.67 V)和加速寿命(112 h)显著提高。在优化工艺条件下,电解30 min后,ESIXSnO_2电极对NH_4~+-N和COD的去除率分别为100%和90%。在实际催化氧化过程中,ESIX-SnO_2电极表面产生更多具有强氧化性的羟基自由基,能够快速氧化氨氮和有机物,实现了污染物的快速无害化去除。